Acer Extensa 390 Features Manual page 26

Getting Familiar with your Computer
1.8 Audio
Standard computer configuration includes 16-bit
high-fidelity stereo audio with further
enhancements that include 3D sound for true
audio immersion. Dual speakers found on both
sides of the display hinge direct sound towards
you which allows for excellent sound output.
Left
Speaker
Besides the built-in speakers, there are audio
ports on the left panel of the computer. See
section 3.6 for more information on connecting
external audio devices.
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Right
Speaker